That depends on what your goal is. If you want to build something cool looking without much pushing power then plastic threads are fine.
If you want to build something with more pushing power then you would want rubber threads, but they could still be not as good as regular omnis, depending on the surface you are planning to be driveing on.
In general, for the competition use, threads don’t have enough friction to outcompete omnis on the foam fields and add too much friction to resist turning and wast motor power. Omnis with optionally locked omnis in the middle row are usually the best choice for the competition.
But if you are trying to build it just for fun here are a couple of classic legacy examples:
